The broad objective of the proposed project is to clarify the molecular pathology of bronchoconstriction, hyperreactivity, and mucous hypersecretion. The investigations proposed here possess implications of potential importance for the comprehension and management of airway diseases ranging from cystic fibrosis to asthma and anaphylaxis. The focus will be the participation of mast cell-derived extracellular proteases and their inhibitors in the initiation and maintenance of pathologic airway states. The abundant granule-associated proteases of several lines of canine mastocytoma cells propogated in athymic mice will be isolated and examined in biochemical detail. Characterization will include the ability to activate or inactivate vasoactive and neuroendocrine peptides found in the lung. Sensitive chromogenic substrates will be developed and tested for their ability to detect active proteases released into secretions of the intact airway or the medium of cultured airway cells, with diverse immunologic and nonimmunologic stimuli. Immunohistochemical reagents prepared from antibodies to purified proteases and inhibitors will be employed to localize these proteins in canine airways and to define functional and molecular bases for mast cell heterogeneity. Effects of purified proteins on epithelial cell functions, gland secretion, and bronchomotor tone will be examined in cultured airway cells, tracheal explants, and allergic dogs. This approach is intended to establish the chemical credibility of actions identified with airway proteases and their inhibitors, in tandem with their physiologic significance. These investigations may suggest specific therapeutic approaches to airway diseases triggered or sustained by protease/inhibitor imbalance or the pathologic release of proteases.